Search

Low-mass active galactic nuclei (AGNs) can provide important constraints on the formation and evolution of supermassive black holes (SMBHs), a central challenge in modern cosmology. To date only small samples of intermediate-mass black holes (IMBHs, $M_{BH}<10^5M_{\odot}$) and 'lesser' supermassive black holes (LSMBHs, $M_{BH}<10^6M_{\odot}$) have been identified. Our present study of NGC 3259 at D=27 Mpc with the Binospec integral field unit spectrograph complemented with Keck Echelle Spectrograph and Imager observations demonstrates the need for and the power of the spectroscopic follow-up. NGC 3259 hosts a black hole with a mass of $M_{BH}=(1.7-4.1)\times10^5M_{\odot}$, inferred from multi-epoch spectroscopic data, that accretes at 1% of the Eddington limit as suggested by the analysis of archival XMM-Newton observations. It is the second nearest low-mass AGN after the archetypal galaxy NGC 4395. The spectroscopic data reveals a variable broad $H\alpha$ profile that is likely the result of asymmetrically distributed broad-line region (BLR) clouds or BLR outflow events. X-ray observations and the absence of an optical power-law continuum suggest partial obscuration of the accretion disk and hot corona by a dust torus. We estimate that the Sloan Digital Sky Survey could only detect similar objects to D=35 Mpc. A detailed photometric analysis of NGC 3259 using HST images provides a central spheroid stellar mass estimate 25 times lower than expected from the $M_{BH}-M^*_{sph}$ relation, making this galaxy a strong outlier. This discrepancy suggests divergent growth pathways for the central black hole and spheroid, potentially influenced by the presence of a bar in the galaxy. Finally, we demonstrate that the DESI and 4MOST surveys will detect low-accretion rate IMBHs and LSMBHs and the sensitivity of future X-ray instruments (such as AXIS and Athena) will secure their classification., Comment: Submitted to A&A; 16 pages, 12 figures

Binospec is a wide-field optical (360 to 1000 nm) spectrograph commissioned at the MMT 6.5m telescope in 2017. In direct imaging mode Binospec addresses twin 8$^\prime$ (wide) by 15$^\prime$ (slit length) fields of view. We describe an optical fiber based integral field unit (IFU) that remaps a 12$^{\prime\prime}$ x 16$^{\prime\prime}$ contiguous region onto two pseudo slits, one in each Binospec channel. The IFU, commissioned in 2023, fits into the space of a standard slit mask frame and can be deployed as desired in a mixed program of slit masks, long slits, and IFU observations. The IFU fibers are illuminated by a hexagonal lenslet array with a 0.6$^{\prime\prime}$ pitch. A separate bundle of sky fibers consists of close-packed bare fibers arranged within an 11.8$^{\prime\prime}$ circular aperture. The 640 IFU fibers and 80 sky fibers have a core diameter of 150$\mu$m, corresponding to 0.90$^{\prime\prime}$. Three gratings are available, 270lpm with R$\sim$2000, 600lpm with R$\sim$5300, and 1000 lpm with R$\sim$6000., Comment: Accepted for publication in PASP, 12 pages, 11 figures, 1 table

Ultra-diffuse galaxies (UDGs) are spatially extended, low surface brightness stellar systems with regular elliptical-like morphology found in large numbers in galaxy clusters and groups. Studies of the internal dynamics and dark matter content of UDGs have been hampered by their low surface brightnesses. We identified a sample of low-mass early-type post-starburst galaxies, `future UDGs' in the Coma cluster still populated with young stars, which will passively evolve into UDGs in the next 5$-$10 Gyr. We collected deep observations for a sample of low-mass early-type galaxies in the Coma cluster using MMT Binospec, which includes present-day and future UDGs. We derived their dark matter content within a half-light radius (70$-$95%) and total dynamical masses ($M_{200}=5.5\cdot10^9-1.4\cdot10^{11} M_{\odot}$) assuming the Burkert density profile and assess how different proposed evolutionary channels affect dark and visible matter in UDGs. We also discuss observational methodology of present and future UDG studies., Comment: accepted to the proceedings of IAU Symposium 379 (Dynamical Masses of Local Group Galaxies), 6 pages, 3 figures

We present preliminary results from our spectroscopic survey of low-luminosity early-type galaxies in the Coma cluster conducted with the Binospec spectrograph at the 6.5~m MMT. From spatially-resolved profiles of internal kinematics and stellar population properties complemented with high-resolution images, we placed several low-luminosity dEs on the fundamental plane in the low-luminosity extension of the available literature data. We also discovered unusual kpc-sized kinematically-decoupled cores in several dwarf galaxies, which had been probably formed before these galaxies entered the cluster., Comment: accepted to the proceedings of IAU Symposium 379 (Dynamical Masses of Local Group Galaxies), 4 pages, 2 figures

HectoMAP is a dense redshift survey of 95,403 galaxies based primarily on MMT spectroscopy with a median redshift $z = 0.345$. The survey covers 54.64 square degrees in a 1.5$^\circ$ wide strip across the northern sky centered at a declination of 43.25$^\circ$. We report the redshift, the spectral indicator D$_{n}$4000, and the stellar mass. The red selected survey is 81\% complete for 55,962 galaxies with $(g-r) > 1$ and $r <20.5$; it is 72\% complete for 32,908 galaxies with $(g-r) > 1$, $(r-i) > 0.5$ and $20.5 < r < 21.3$. Comparison of the survey basis SDSS photometry with the HSC-SSP photometry demonstrates that HectoMAP provides complete magnitude limited surveys based on either photometric system. We update the comparison between the HSC-SSP photometric redshifts with HectoMAP spectroscopic redshifts; the comparison demonstrates that the HSC-SSP photometric redshifts have improved between the second and third data releases. HectoMAP is a foundation for examining the quiescent galaxy population (63\% of the survey), clusters of galaxies, and the cosmic web. HectoMAP is completely covered by the HSC-SSP survey, thus enabling a variety of strong and weak lensing investigations., Comment: Accepted for publication in The Astrophysical Journal. 22 pages, 16 figures, 3 tables. The full dataset for HectoMAP will be available when the paper is published

Low-mass early-type galaxies, including dwarf spheroidals (dSph) and brighter dwarf ellipticals (dE), dominate the galaxy population in groups and clusters. Recently, an additional early-type population of more extended ultradiffuse galaxies (UDGs) has been identified, sparking a discussion on the potential morphological and evolutionary connections between the three classifications. Here, we present the first measurements of spatially resolved stellar kinematics from deep integrated-light spectra of KDG 64 (UGC 5442), a large dSph galaxy in the M 81 group. From these data, we infer stellar population properties and dark matter halo parameters using Jeans dynamical modelling. We find an old, metal-poor stellar population with no young stars and a dark matter mass fraction of ~ 90 per cent within the half-light radius. These properties and the position of KDG 64 on the Fundamental Plane indicate that it is a local analogue of smaller UDGs in the Coma and Virgo clusters and is probably a transitional dSph-UDG object. Its evolutionary path cannot be uniquely established from the existing data, but we argue that supernovae feedback and tidal heating played key roles in shaping KDG 64., Comment: 10 pages, 5 figures, published in MNRAS

Faint extended elliptically-shaped ultra-diffuse galaxies and slightly brighter and more compact dwarf elliptical and lenticular stellar systems are common in galaxy clusters. Their poorly constrained evolutionary paths can be studied by identifying young ultra-diffuse galaxy and dwarf elliptical analogs populated with bright, massive stars. Using data mining we identified 11 such low-mass ($2\times10^8

We report on the status of the Tierras Observatory, a refurbished 1.3-m ultra-precise fully-automated photometer located at the F. L. Whipple Observatory atop Mt. Hopkins, Arizona. Tierras is designed to limit systematic errors, notably precipitable water vapor (PWV), to 250 ppm, enabling the characterization of terrestrial planet transits orbiting $< 0.3 \, R_{\odot}$ stars, as well as the potential discovery of exo-moons and exo-rings. The design choices that will enable our science goals include: a four-lens focal reducer and field-flattener to increase the field-of-view of the telescope from a $11.94'$ to a $0.48^{\circ}$ side; a custom narrow bandpass ($40.2$ nm FWHM) filter centered around $863.5$ nm to minimize PWV errors known to limit ground-based photometry of red dwarfs; and a deep-depletion $4K \times 4K$ CCD with a 300ke-full well and QE$>85\%$ in our bandpass, operating in frame transfer mode. We are also pursuing the design of a set of baffles to minimize the significant amount of scattered light reaching the image plane. Tierras will begin science operations in early 2021., Comment: SPIE Astronomical Telescopes & Instrumentation 2020 Proceedings (11445-168), 20 pages, 11 figures

We announce the public release of 141,531 moderate-dispersion optical spectra of 72,247 objects acquired over the past 25 years with the FAST Spectrograph on the Fred L. Whipple Observatory 1.5-meter Tillinghast telescope. We describe the data acquisition and processing so that scientists can understand the spectra. We highlight some of the largest FAST survey programs, and make recommendations for use. The spectra have been placed in a Virtual Observatory accessible archive and are ready for download., Comment: 17 pages, 18 figures, 8 tables

HectoMAP is a dense, red-selected redshift survey to a limiting $r = 21.3$ covering 55 square degrees in a contiguous 1.5$^\circ$ strip across the northern sky. This region is also covered by the Subaru/Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) photometric survey enabling a range of applications that combine a dense foreground redshift survey with both strong and weak lensing maps. The median redshift of HectoMAP exceeds 0.3 throughout the survey region and the mean density of the redshift survey is $\sim 2000$ galaxies deg$^{-2}$. Here we report a total of 17,313 redshifts in a first data release covering 8.7 square degrees. We include the derived quantities D$_{n}4000$ and stellar mass for nearly all of the objects. Among these galaxies, 8117 constitute a 79\% complete red-selected subsample with $r \leq 20.5$ and an additional 4318 constitute a 68\% complete red-selected subsample with $20.5 < r < 21.3$. As examples of the strengths of HectoMAP data we discuss two applications: refined membership of redMaPPer photometrically selected clusters and a test of HSC photometric redshifts. We highlight a remarkable redMaPPer strong lensing system. The comparison of photometric redshifts with spectroscopic redshifts in a dense survey uncovers subtle systematic issues in the photometric redshifts., Comment: 21 pages, 16 figures, ApJ submitted

We measure the central stellar velocity dispersion function for quiescent galaxies in a set of nine northern clusters in the redshift range $0.18 < z < 0.29$ and with strong lensing arcs in Hubble Space Telescope images. The velocity dispersion function links galaxies directly to their dark matter halos. From dense SDSS and MMT/Hectospec spectroscopy we identify $231 - 479$ spectroscopic members in each cluster. We derive physical properties of cluster members including redshift, $D_{n}4000$, and central stellar velocity dispersion and we include a table of these measurements for 3419 cluster members. We construct the velocity dispersion functions for quiescent galaxies with $D_{n}4000 > 1.5$ and within $R_{200}$. The cluster velocity dispersion functions all show excesses at $\sigma \gtrsim 250 km s^{-1}$ compared to the field velocity dispersion function. The velocity dispersion function slope at large velocity dispersion ($\sigma > 160 km s^{-1}$) is steeper for more massive clusters, consistent with the trend observed for cluster luminosity functions. The spatial distribution of galaxies with large velocity dispersion at radii larger than $R_{200}$ further underscores the probable major role of dry mergers in the growth of massive cluster galaxies during cluster assembly., Comment: 16 pages, 12 figures, Accepted for publication in the ApJ

Spectroscopic studies of low-luminosity early-type galaxies are essential to understand their origin and evolution but remain challenging because of low surface brightness levels. We describe an observational campaign with the new high-throughput Binospec spectrograph at the 6.5-m MMT. It targets a representative sample of dwarf elliptical (dE), ultra-diffuse (UDG), and dwarf spheroidal (dSph) galaxies. We outline our data analysis approach that features (i) a full spectrophotometric fitting to derive internal kinematics and star formation histories of galaxies; (ii) two-dimensional light profile decomposition; (iii) Jeans anisotropic modelling to assess their internal dynamics and dark matter content. We present first results for 9 UDGs in the Coma cluster and a nearby dSph galaxy, which suggest that a combination of internal (supernovae feedback) and environmental (ram-pressure stripping, interactions) processes can explain observed properties of UDGs and, therefore, establish an evolutionary link between UDGs, dSph, and dE galaxies., Comment: Conference proceeding for the IAU Symposium 355 "The Realm of the Low Surface Brightness Universe" held in Tenerife, Spain, July 8-12, 2019

The dominant physical processes responsible for the formation and longevity of giant gaseous and stellar discs in galaxies remain controversial. Although they are rare (less than 10 confirmed as of now), giant low-surface brightness (gLSB) discy galaxies provide interesting insights given their extreme nature. We describe observations of UGC 1378 including deep spectroscopy with the Russian 6m telescope and multi-band imaging with Binospec at the MMT. Galaxy UGC 1378 has both high surface brightness and an extended low surface brightness discs. Our stellar velocity dispersion data for the high-surface brightness, Milky Way-sized, disc appears inconsistent with a recent major merger, a widely discussed formation scenario for the very extended low surface brightness disc. We estimate the star formation rates (SFR) from archival Wide-Field Infrared Survey Explorer data. The SFR surface density in the LSB disc is low relative to its gas density, consistent with recent gas accretion. We argue that the unusually large size of UGC 1378's disc may be the product of a rich gas reservoir (e.g. a cosmic filament) and an isolated environment that has preserved the giant disc., Comment: Accepted for publication in MNRAS, 10 pages, 7 figures, 3 tables

Modern theories of galaxy formation predict that the Galactic stellar halo was hierarchically assembled from the accretion and disruption of smaller systems. This hierarchical assembly is expected to produce a high degree of structure in the combined phase and chemistry space; this structure should provide a relatively direct probe of the accretion history of our Galaxy. Revealing this structure requires precise 3D positions (including distances), 3D velocities, and chemistry for large samples of stars. The Gaia satellite is delivering proper motions and parallaxes for >1 billion stars to G~20. However, radial velocities and metallicities will only be available to G~15, which is insufficient to probe the outer stellar halo (>10 kpc). Moreover, parallaxes will not be precise enough to deliver high-quality distances for stars beyond ~10 kpc. Identifying accreted systems throughout the stellar halo therefore requires a large ground-based spectroscopic survey to complement Gaia. Here we provide an overview of the H3 Stellar Spectroscopic Survey, which will deliver precise stellar parameters and spectrophotometric distances for 200,000 stars to r=18. Spectra are obtained with the Hectochelle instrument at the MMT, which is configured for the H3 Survey to deliver resolution R~23,000 spectra covering the wavelength range 5150A-5300A. The survey is optimized for stellar halo science and therefore focuses on high Galactic latitude fields (|b|>30 deg.), sparsely sampling 15,000 sq. degrees. Targets are selected on the basis of Gaia parallaxes, enabling very efficient selection of bone fide halo stars. The survey began in the Fall of 2017 and has collected 88,000 spectra to-date. All of the data, including the derived stellar parameters, will eventually be made publicly available via the survey website: h3survey.rc.fas.harvard.edu., Comment: 14 pages, 15 figures. Resubmitted to ApJ after responding to referee

Binospec is a high throughput, 370 to 1000 nm, imaging spectrograph that addresses two adjacent 8' by 15' fields of view. Binospec was commissioned in late 2017 at the f/5 focus of the 6.5m MMT and is now available to all MMT observers. Aperture masks cut from stainless steel with a laser cutter are used to define the entrance apertures that range from 15' long slits to hundreds of 2" slitlets. System throughputs, including the MMT's mirrors and the f/5 wide-field corrector peak at ~30%. Three reflection gratings, duplicated for the two beams, provide resolutions ($\lambda$/$\Delta \lambda$) between 1300 and $>$5000 with a 1" wide slit. Two through-the-mask guiders are used for target acquisition, mask alignment, guiding, and precision offsets. A full-time Shack-Hartmann wave front sensor allows continuous adjustment of primary mirror support forces, telescope collimation and focus. Active flexure control maintains spectrograph alignment and focus under varying gravity and thermal conditions., Comment: PASP in press; 45 pages, 59 figures

Binospec is a high-throughput, 370 to 1000 nm, imaging spectrograph that addresses two adjacent 8' by 15' fields of view. Binospec was commissioned in late 2017 at the f/5 focus of the 6.5m MMT and is now available to all MMT observers. Here we describe the Binospec software used for observation planning, instrument control, and data reduction. The software and control systems incorporate a high level of automation to minimize observer workload. Instrument configuration and observation sequencing is implemented using a database-driven approach to maximize observatory efficiency. A web-based interface allows users to define observations, monitor status, and retrieve data products., Comment: PASP in press; 22 pages; 12 figures

Ultra-diffuse galaxies (UDGs) are spatially extended, low surface brightness stellar systems with regular elliptical-like morphology found in a wide range of environments. Studies of the internal dynamics and dark matter content of UDGs that would elucidate their formation and evolution have been hampered by their low surface brightnesses. Here we present spatially resolved velocity profiles, stellar velocity dispersions, ages and metallicities for 9 UDGs in the Coma cluster. We use intermediate-resolution spectra obtained with Binospec, the MMT's new high-throughput optical spectrograph. We derive dark matter fractions between 50~\%\ and 90~\% within the half-light radius using Jeans dynamical models. Three galaxies exhibit major axis rotation, two others have highly anisotropic stellar orbits, and one shows signs of triaxiality. In the Faber--Jackson and mass--metallicity relations, the 9 UDGs fill the gap between cluster dwarf elliptical (dE) and fainter dwarf spheroidal (dSph) galaxies. Overall, the observed properties of all 9 UDGs can be explained by a combination of internal processes (supernovae feedback) and environmental effects (ram-pressure stripping, interaction with neighbors). These observations suggest that UDGs and dEs are members of the same galaxy population., Comment: Accepted to ApJ, 14 pages, 3 figures, 1 table

A rich spectroscopic census of members of the local massive cluster Abell 2029 includes 1215 members of A2029 and its two infalling groups, A2033 and a Southern Infalling Group (SIG). The two infalling groups are identified in spectroscopic, X-ray and weak lensing maps. We identify active galactic nuclei (AGN), star-forming galaxies, E+A galaxies, and quiescent galaxies based on the spectroscopy. The fractions of AGN and post-starburst E+A galaxies in A2029 are similar to those of other clusters. We derive the stellar mass ($M_{*}$)-metallicity of A2029 based on 227 star-forming members; A2029 members within $10^{9} M_{\odot} < M _{*} < 10^{9.5} M_{\odot}$ are more metal rich than SDSS galaxies within the same mass range. We utilize the spectroscopic index $D_{n}4000$, a strong age indicator, to trace past and future evolution of the A2029 system. The median $D_{n}4000$ of the members decreases as the projected clustercentric distance increases for all three subsystems. The $D_{n}4000 - M_{*}$ relations of the members in A2029 and its two infalling groups differ significantly indicating the importance of stochastic effects for understanding the evolution of cluster galaxy populations. In the main cluster, an excess around $D_{n}4000 \sim 1.8$ indicates that some A2029 members became quiescent galaxies 2-3 Gyr ago consistent with the merger epoch of the X-ray sloshing pattern., Comment: 17 pages, 11 figures, submitted to ApJ

We describe the hCOSMOS redshift survey of the COSMOS field conducted with the Hectospec spectrograph on the MMT. In the central 1~deg$^2$, the hCOS20.6 subset of the survey is $>90\%$ complete to a limiting $r=20.6$. The hCOSMOS survey includes 1701 new redshifts in the COSMOS field. We also use the total of 4362 new and remeasured objects to derive the age sensitive D$_n4000$ index over the entire redshift interval $0.001\lesssim z\lesssim0.6$. For $85\%$ of the quiescent galaxies in hCOS20.6, we measure the central line-of-sight velocity dispersion. To explore potential uses of this survey, we combine previously measured galaxy sizes, profiles and stellar masses with the spectroscopy. The comparison reveals the known relations among structural, kinematic, and stellar population properties. We also compare redshift and D$_n4000$ distributions of hCOS20.6 galaxies with SHELS; a complete spectroscopic survey of 4~deg$^2$ observed to the same depth. The redshift distributions in the two fields are very different but the D$_n4000$ distribution is remarkably similar. The relation between velocity dispersion and stellar mass for massive hCOS20.6 galaxies is consistent with the local relation from SDSS. Using measured velocity dispersions, we test a photometric proxy calibrated to galaxies in the local universe. The systematic differences between the measured and photometric proxy velocity dispersions are correlated with galaxy dynamical and stellar population properties highlighting the importance of direct spectroscopic measurements., Comment: ApJS accepted. Complete Table 2 in a machine-readable format is available at https://www.cfa.harvard.edu/~hzahid/Data_files/Table2_MR.dat

Based on an extensive redshift survey for galaxy cluster Abell 2029 and Coma, we measure the luminosity functions (LFs), stellar mass functions (SMFs) for the entire cluster member galaxies. Most importantly, we measure the velocity dispersion functions (VDFs) for quiescent members. The MMT/Hectospec redshift survey for galaxies in A2029 identifies 982 spectroscopic members; for 838 members we derive the central velocity dispersion from the spectroscopy. Coma is the only other cluster surveyed as densely. The LFs, SMFs and VDFs for A2029 and Coma are essentially identical. The SMFs of the clusters are consistent with simulations. The A2029 and Coma VDFs for quiescent galaxies have a significantly steeper slope than those of field galaxies for velocity dispersion $\lesssim 100$ km s$^{-1}$. The cluster VDFs also exceed the field at velocity dispersion $\gtrsim 250$ km s$^{-1}$. The differences between cluster and field VDFs are potentially important tests of simulations and of the formation of structure in the universe., Comment: 16 pages, 18 figures, 4 tables, submitted to ApJ

We examine the relation between stellar mass and central stellar velocity dispersion-the M-sigma relation-for massive quiescent galaxies at z<0.7. We measure the local relation from the Sloan Digital Sky Survey and the intermediate redshift relation from the Smithsonian Hectospec Lensing Survey. Both samples are highly complete (>85%) and we consistently measure the stellar mass and velocity dispersion for the two samples. The M-sigma relation and its scatter are independent of redshift with sigma ~ M^0.3 for M>10^10.3 M_solar. The measured slope of the M-sigma relation is the same as the scaling between the total halo mass and the dark matter halo velocity dispersion obtained by N-body simulations. This consistency suggests that massive quiescent galaxies are virialized systems where the central dark matter concentration is either a constant or negligible fraction of the stellar mass. The relation between the total galaxy mass (stellar + dark matter) and the central stellar velocity dispersion is consistent with the observed relation between the total mass of a galaxy cluster and the velocity dispersion of the cluster members. This result suggests that the central stellar velocity dispersion is directly proportional to the velocity dispersion of the dark matter halo. Thus the central stellar velocity dispersion is a fundamental, directly observable property of galaxies that may robustly connect galaxies to dark matter halos in N-body simulations. To interpret the results further in the context of Lambda-CDM, it would be useful to analyze the relationship between the velocity dispersion of stellar particles and the velocity dispersion characterizing their dark matter halos in high-resolution cosmological hydrodynamic simulations., Comment: 15 pages, 14 figures. To be published in ApJ. Updated to accepted version

The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey. Both fields are more than 94% complete to a Galactic extinction corrected R0 = 20.2. Here we describe the redshift survey of the F1 field centered at R.A. = 00h53m25.3s and Decl = 12d33m55s; like F2, the F1 field covers 4 sq deg. The redshift survey of the F1 field includes 9426 new galaxy redshifts measured with Hectospec on the MMT (published here). As a guide to future uses of the combined survey we compare the mass metallicity relation and the distributions of D4000 as a function of stellar mass and redshift for the two fields. The mass-metallicity relations differ by an insignificant 1.6 sigma. For galaxies in the stellar mass range 1.e10 to 1.e11 MSun, the increase in the star-forming fraction with redshift is remarkably similar in the two fields. The seemingly surprising 31-38% difference in the overall galaxy counts in F1 and F2 is probably consistent with the expected cosmic variance given the subtleties of the relative systematics in the two surveys. We also review the Deep Lens Survey cluster detections in the two fields: poorer photometric data for F1 precluded secure detection of the single massive cluster at z = 0.35 that we find in SHELS. Taken together the two fields include 16,055 redshifts for galaxies with R0 <= 20.2 and 20,754 redshifts for galaxies with R <= 20.6. These dense surveys in two well-separated fields provide a basis for future investigations of galaxy properties and large-scale structure., Comment: 24 pages, 6 tables, 13 figures; ApJS, accepted; full data tables available in journal upon publication

HectoMAP is a dense redshift survey of red galaxies covering a 53 $deg^{2}$ strip of the northern sky. HectoMAP is 97\% complete for galaxies with $r<20.5$, $(g-r)>1.0$, and $(r-i)>0.5$. The survey enables tests of the physical properties of large-scale structure at intermediate redshift against cosmological models. We use the Horizon Run 4, one of the densest and largest cosmological simulations based on the standard $\Lambda$ Cold Dark Matter ($\Lambda$CDM) model, to compare the physical properties of observed large-scale structures with simulated ones in a volume-limited sample covering 8$\times10^6$ $h^{-3}$ Mpc$^3$ in the redshift range $0.22

We examine the evolution of the relation between stellar mass surface density, velocity dispersion and half-light radius$-$the stellar mass fundamental plane$-$for quiescent galaxies at $z<0.6$. We measure the local relation from galaxies in the Sloan Digital Sky Survey and the intermediate redshift relation from $\sim500$ quiescent galaxies with stellar masses $10 \lesssim \mathrm{log}(M_\ast/M_\odot) \lesssim 11.5$. Nearly half of the quiescent galaxies in our intermediate redshift sample are compact. After accounting for important selection and systematic effects, the velocity dispersion distribution of galaxies at intermediate redshifts is similar to galaxies in the local universe. Galaxies at $z<0.6$ appear to be smaller ($\lesssim0.1$ dex) than galaxies in the local sample. The orientation of the stellar mass fundamental plane is independent of redshift for massive quiescent galaxies at $z<0.6$ and the zero-point evolves by $\sim 0.04$ dex. Compact quiescent galaxies fall on the same relation as the extended objects. We confirm that compact quiescent galaxies are the tail of the size and mass distribution of the normal quiescent galaxy population., Comment: 12 pages, 8 figures. Updated to accepted version to appear in ApJ

We describe the new spectroscopic data reduction pipeline for the multi-object MMT/Magellan Infrared Spectrograph. The pipeline is implemented in idl as a stand-alone package and is publicly available in both stable and development versions. We describe novel algorithms for sky subtraction and correction for telluric absorption. We demonstrate that our sky subtraction technique reaches the Poisson limit set by the photon statistics. Our telluric correction uses a hybrid approach by first computing a correction function from an observed stellar spectrum, and then differentially correcting it using a grid of atmosphere transmission models for the target airmass value. The pipeline provides a sufficient level of performance for real time reduction and thus enables data quality control during observations. We reduce an example dataset to demonstrate the high data reduction quality., Comment: PASP in press, 14 pages, 6 figures

The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey to a limiting R = 20.6. Here we describe the redshift survey of the F2 field (R.A.$_{2000}$ = 09$^h$19$^m$32.4$^s$ and Decl.$_{2000}$ = +30$^{\circ}$00$^{\prime}$00$^{\prime\prime}$). The survey includes 16,294 new redshifts measured with the Hectospec on the MMT. The resulting survey of the 4 deg$^2$ F2 field is 95\% complete to R = 20.6, currently the densest survey to this magnitude limit. The median survey redshift is $ z = 0.3$; the survey provides a view of structure in the range 0.1 $ \lesssim z \lesssim 0.6$. A movie displays the large-scale structure in the survey region. We provide a redshift, spectral index D$_n$4000, and stellar mass for each galaxy in the survey. We also provide a metallicity for each galaxy in the range 0.2 $< z <0. 38$. To demonstrate potential applications of the survey, we examine the behavior of the index D$_n$4000 as a function of galaxy luminosity, stellar mass, and redshift. The known evolutionary and stellar mass dependent properties of the galaxy population are cleanly evident in the data. We also show that the mass-metallicity relation previously determined from these data is robust to the analysis approach., Comment: 45 pages, 16 figures, 7 tables. Data will be available only when the paper is published in Astrophysical Journal Supplements (now submitted). Movie and full resolution figures are available at https://www.cfa.harvard.edu/~mjg/f6movie.mp4 and https://www.cfa.harvard.edu/~mjg/SHELS.pdf

We describe a robust technique based on the ULySS IDL code for measuring velocity dispersions of galaxies observed with the MMT's fiber-fed spectrograph, Hectospec. This procedure is applicable to all Hectospec spectra having a signal-to-noise >5 and weak emission lines. We estimate the internal error in the Hectospec velocity dispersion measurements by comparing duplicate measurements of 171 galaxies. For a sample of 984 galaxies with a median z=0.10, we compare velocity dispersions measured by Hectospec through a 1.5 arcsec diameter optical fiber with those measured by the Sloan Digital Sky Survey (SDSS) and Baryon Oscillation Spectral Survey (BOSS) through 3 arcsec and 2 arcsec diameter optical fibers, respectively. The systematic differences between the Hectospec and the SDSS/BOSS measurements are <7% for velocity dispersions between 100 and 300 km/s, the differences are no larger than the differences among the three BOSS velocity dispersion reductions. We analyze the scatter about the fundamental plane and find no significant redshift dependent systematics in our velocity dispersion measurements to z~0.6. This analysis also confirms our estimation of the measurement errors. In one hour in good conditions, we demonstrate that we achieve 30 km/s velocity dispersion errors for galaxies with an SDSS r fiber magnitude of 21., Comment: 8 figures

We relate transitions in galaxy structure and gas content to refueling, here defined to include both the external gas accretion and the internal gas processing needed to renew reservoirs for star formation. We analyze two z=0 data sets: a high-quality ~200-galaxy sample (the Nearby Field Galaxy Survey, data release herein) and a volume-limited ~3000-galaxy sample with reprocessed archival data. Both reach down to baryonic masses ~10^9Msun and span void-to-cluster environments. Two mass-dependent transitions are evident: (i) below the "gas-richness threshold" scale (V~125km/s), gas-dominated quasi-bulgeless Sd--Im galaxies become numerically dominant, while (ii) above the "bimodality" scale (V~200km/s), gas-starved E/S0s become the norm. Notwithstanding these transitions, galaxy mass (or V as its proxy) is a poor predictor of gas-to-stellar mass ratio M_gas/M_*. Instead, M_gas/M_* correlates well with the ratio of a galaxy's stellar mass formed in the last Gyr to its preexisting stellar mass, such that the two ratios have numerically similar values. This striking correspondence between past-averaged star formation and current gas richness implies routine refueling of star-forming galaxies on Gyr timescales. We argue that this refueling underlies the tight M_gas/M_* vs. color correlations often used to measure "photometric gas fractions." Furthermore, the threshold and bimodality scale transitions reflect mass-dependent demographic shifts between three refueling regimes --- accretion dominated, processing dominated, and quenched. In this picture, gas-dominated dwarfs are explained not by inefficient star formation but by overwhelming gas accretion, which fuels stellar mass doubling in <~1Gyr. Moreover, moderately gas-rich bulged disks such as the Milky Way are transitional, becoming abundant only in the narrow range between the threshold and bimodality scales., Comment: ApJ, accepted, 28 pages including 12 figures and Table 2; data for Table 1 available at http://www.physics.unc.edu/~sheila/k13_table1.csv

Weak lensing provides an important route toward collecting samples of clusters of galaxies selected by mass. Subtle systematic errors in image reduction can compromise the power of this technique. We use the B-mode signal to quantify this systematic error and to test methods for reducing this error. We show that two procedures are efficient in suppressing systematic error in the B-mode: (1) refinement of the mosaic CCD warping procedure to conform to absolute celestial coordinates and (2) truncation of the smoothing procedure on a scale of 10$^{\prime}$. Application of these procedures reduces the systematic error to 20% of its original amplitude. We provide an analytic expression for the distribution of the highest peaks in noise maps that can be used to estimate the fraction of false peaks in the weak lensing $\kappa$-S/N maps as a function of the detection threshold. Based on this analysis we select a threshold S/N = 4.56 for identifying an uncontaminated set of weak lensing peaks in two test fields covering a total area of $\sim 3$deg$^2$. Taken together these fields contain seven peaks above the threshold. Among these, six are probable systems of galaxies and one is a superposition. We confirm the reliability of these peaks with dense redshift surveys, x-ray and imaging observations. The systematic error reduction procedures we apply are general and can be applied to future large-area weak lensing surveys. Our high peak analysis suggests that with a S/N threshold of 4.5, there should be only 2.7 spurious weak lensing peaks even in an area of 1000 deg$^2$ where we expect $\sim$ 2000 peaks based on our Subaru fields., Comment: 30 pages, Submitted to Astrophysical Journal

We calculate the stellar mass-metallicity relation at five epochs ranging to z~2.3. We quantify evolution in the shape of the mass-metallicity relation as a function of redshift; the mass-metallicity relation flattens at late times. There is an empirical upper limit to the gas-phase oxygen abundance in star-forming galaxies that is independent of redshift. From examination of the mass-metallicity relation and its observed scatter we show that the flattening at late times is a consequence of evolution in the stellar mass where galaxies enrich to this empirical upper metallicity limit; there is also evolution in the fraction of galaxies at a fixed stellar mass that enrich to this limit. The stellar mass where metallicities begin to saturate is ~0.7 dex smaller in the local universe than it is at z~0.8., Comment: 6 pages, 2 figures. Accepted for publication in ApJ Letters

We describe principal components of the new spectroscopic data pipeline for the multi-object MMT/Magellan Infrared Spectrograph (MMIRS). The pipeline is implemented in IDL and C++. The performance of the data processing algorithms is sufficient to reduce a single dataset in 2--3 min on a modern PC workstation so that one can use the pipeline as a quick-look tool during observations. We provide an example of the spectral data processed by our pipeline and demonstrate that the sky subtraction quality gets close to the limits set by the Poisson photon statistics., Comment: 4 pages, 2 figures, to be published in the proceedings of the ADASS-XXII conference

The MMT and Magellan infrared spectrograph (MMIRS) is a cryogenic multiple slit spectrograph operating in the wavelength range 0.9-2.4 micron. MMIRS' refractive optics offer a 6.9 by 6.9 arcmin field of view for imaging with a spatial resolution of 0.2 arcsec per pixel on a HAWAII-2 array. For spectroscopy, MMIRS can be used with long slits up to 6.9 arcmin long, or with custom slit masks having slitlets distributed over a 4 by 6.9 arcmin area. A range of dispersers offer spectral resolutions of 800 to 3000. MMIRS is designed to be used at the f/5 foci of the MMT or Magellan Clay 6.5m telescopes. MMIRS was commissioned in 2009 at the MMT and has been in routine operation at the Magellan Clay Telescope since 2010. MMIRS is being used for a wide range of scientific investigations from exoplanet atmospheres to Ly-alpha emitters., Comment: 43 pages, including 11 figures, accepted for publication in PASP

We use a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), covering a 4 square degree region of a deep imaging survey, the Deep Lens Survey (DLS), to study the optical spectral properties of Wide-field Infrared Survey Explorer (WISE) 22 \mu m-selected galaxies. Among 507 WISE 22 \mu m-selected sources with (S/N)_{22\mu m}>3 (\simS_{22\mu m}>2.5 mJy), we identify the optical counterparts of 481 sources (\sim98%) at R<25.2 in the very deep, DLS R-band source catalog. Among them, 337 galaxies at R<21 have SHELS spectroscopic data. Most of these objects are at z<0.8. The infrared (IR) luminosities are in the range 4.5x10^8 (L_sun) < L_{IR} < 5.4x10^{12} (L_sun). Most 22 \mu m-selected galaxies are dusty star-forming galaxies with a small (<1.5) 4000 \AA break. The stacked spectra of the 22 \mu m-selected galaxies binned in IR luminosity show that the strength of the [O III] line relative to H\beta grows with increasing IR luminosity. The optical spectra of the 22 \mu m-selected galaxies also show that there are some (\sim2.8%) unusual galaxies with very strong [Ne III] \lambda 3869, 3968 emission lines that require hard ionizing radiation such as AGN or extremely young massive stars. The specific star formation rates (sSFRs) derived from the 3.6 and 22 \mu m flux densities are enhanced if the 22 \mu m-selected galaxies have close late-type neighbors. The sSFR distribution of the 22 \mu m-selected galaxies containing active galactic nuclei (AGNs) is similar to the distribution for star-forming galaxies without AGNs. We identify 48 dust-obscured galaxy (DOG) candidates with large (\gtrsim1000) mid-IR to optical flux density ratio. The combination of deep photometric and spectroscopic data with WISE data suggests that WISE can probe the universe to z\sim2., Comment: 18 pages, 17 figures. To appear in ApJ

SHELS (Smithsonian Hectospec Lensing Survey) is a dense redshift survey covering a 4 square degree region to a limiting R = 20.6. In the construction of the galaxy catalog and in the acquisition of spectroscopic targets, we paid careful attention to the survey completeness for lower surface brightness dwarf galaxies. Thus, although the survey covers a small area, it is a robust basis for computation of the slope of the faint end of the galaxy luminosity function to a limiting M_R = -13.3 + 5logh. We calculate the faint end slope in the R-band for the subset of SHELS galaxies with redshif ts in the range 0.02 <= z < 0.1, SHELS_{0.1}. This sample contains 532 galaxies with R< 20.6 and with a median surface brightness within the half light radius of SB_{50,R} = 21.82 mag arcsec^{-2}. We used this sample to make one of the few direct measurements of the dependence of the faint end of the galaxy luminosity function on surface brightness. For the sample as a whole the faint end slope, alpha = -1.31 +/- 0.04, is consistent with both the Blanton et al. (2005b) analysis of the SDSS and the Liu et al. (2008) analysis of the COSMOS field. This consistency is impressive given the very different approaches of th ese three surveys. A magnitude limited sample of 135 galaxies with optical spectroscopic reds hifts with mean half-light surface brightness, SB_{50,R} >= 22.5 mag arcsec^{-2} is unique to SHELS_{0.1}. The faint end slope is alpha_{22.5} = -1.52+/- 0.16. SHELS_{0.1} shows that lower surface brightness objects dominate the faint end slope of the l uminosity function in the field, underscoring the importance of surface brightness limits in evaluating measurements of the faint end slope and its evolution., Comment: 34 pages, 13 figures, 3 tables, Astronomical Journal, in press (updated based on review)

We use a dense redshift survey in the foreground of the Subaru GTO2deg^2 weak lensing field (centered at $\alpha_{2000}$ = 16$^h04^m44^s$;$\delta_{2000}$ =43^\circ11^{\prime}24^{\prime\prime}$) to assess the completeness and comment on the purity of massive halo identification in the weak lensing map. The redshift survey (published here) includes 4541 galaxies; 4405 are new redshifts measured with the Hectospec on the MMT. Among the weak lensing peaks with a signal-to-noise greater that 4.25, 2/3 correspond to individual massive systems; this result is essentially identical to the Geller et al. (2010) test of the Deep Lens Survey field F2. The Subaru map, based on images in substantially better seeing than the DLS, enables detection of less massive halos at fixed redshift as expected. We demonstrate that the procedure adopted by Miyazaki et al. (2007) for removing some contaminated peaks from the weak lensing map improves agreement between the lensing map and the redshift survey in the identification of candidate massive systems., Comment: Astrophysical Journal accepted version

The Smithsonian Hectospec Lensing Survey (SHELS) is a magnitude limited spectroscopically complete survey for R<=21.0 covering 4 square degrees. SHELS provides a large sample (15,513) of flux calibrated spectra. The wavelength range covered by the spectra allows empirical determination of k-corrections for the g- and r-band from z=0 to ~0.68 and 0.33, respectively, based on large samples of spectra. We approximate the k-corrections using only two parameters in a standard way: Dn4000 and redshift. We use Dn4000 rather than the standard observed galaxy color because Dn4000 is a redshift independent tracer of the stellar population of the galaxy. Our approximations for the k-corrections using Dn4000 are as good as (or better than) those based on observed galaxy color (g-r) (sigma of the scatter is ~0.08 mag). The approximations for the k-corrections are available in an on-line calculator. Our results agree with previously determined analytical approximations from single stellar population (SSP) models fitted to multi-band optical and near-infrared photometry for galaxies with a known redshift. Galaxies with the smallest Dn4000-the galaxies with the youngest stellar populations-are always attenuated and/or contain contributions from older stellar populations. We use simple single SSP fits to the SHELS spectra to study the influence of emission lines on the k-correction. The effects of emission lines can be ignored for rest-frame equivalent widths <~ 100 A depending on required photometric accuracy. We also provide analytic approximations to the k-corrections determined from our model fits for z<=0.7 as a function of redshift and Dn4000 for ugriz and UBVRI (sigma of the scatter is typically ~0.10 mag). Again, the approximations using Dn4000 are as good (or better than) those based on a suitably chosen observed galaxy color. We provide all analytical approximations in an on-line calculator., Comment: 48 pages in total (includes 19 figures, 25 tables). Published in PASP. Version with high resolution figures available at http://www.cfa.harvard.edu/~ewestra/publications/. Online calculator at http://tdc-www.cfa.harvard.edu/instruments/hectospec/progs/EOK/. Tables with coefficients differ slightly from first astro-ph version, results barely changed

We measure the strength, frequency, and timescale of tidally triggered star formation at redshift z=0.08-0.38 in a spectroscopically complete sample of galaxy pairs drawn from the magnitude-limited redshift survey of 9,825 Smithsonian Hectospec Lensing Survey (SHELS) galaxies with R<20.3. To examine the evidence for tidal triggering, we identify a volume-limited sample of major (|\Delta M_R|<1.75, corresponding to mass ratio >1/5) pair galaxies with $M_R < -20.8 in the redshift range z=0.08-0.31. The size and completeness of the spectroscopic survey allows us to focus on regions of low local density. The spectrophotometric calibration enables the use of the 4000 Ang break (D_n4000), the H\alpha specific star formation rate (SSFR_{H\alpha}), and population models to characterize the galaxies. We show that D_n4000 is a useful population classification tool; it closely tracks the identification of emission line galaxies. The sample of major pair galaxies in regions of low local density with low D_n4000 demonstrates the expected anti-correlation between pair-wise projected separation and a set of star formation indicators explored in previous studies. We measure the frequency of triggered star formation by comparing the SSFR_{H\alpha} in the volume-limited sample in regions of low local density: 32 +/-7% of the major pair galaxies have SSFR_{H\alpha} at least double the median rate of the unpaired field galaxies. Comparison of stellar population models for pair and for unpaired field galaxies implies a timescale for triggered star formation of ~300-400 Myr., Comment: 25 pages, 15 figures. Accepted to AJ

Weak lensing surveys are emerging as an important tool for the construction of "mass selected" clusters of galaxies. We evaluate both the efficiency and completeness of a weak lensing selection by combining a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), with a weak lensing map from the Deep Lens Survey (DLS). SHELS includes 11,692 redshifts for galaxies with R < 20.6 in the four square degree DLS field; the survey is a solid basis for identifying massive clusters of galaxies with redshift z < 0.55. The range of sensitivity of the redshift survey is similar to the range for the DLS convergence map. Only four the twelve convergence peaks with signal-to-noise > 3.5 correspond to clusters of galaxies with M > 1.7 x 10^14 solar masses. Four of the eight massive clusters in SHELS are detected in the weak lensing map yielding a completeness of roughly 50%. We examine the seven known extended cluster x-ray sources in the DLS field: three can be detected in the weak lensing map, three should not be detected without boosting from superposed large-scale structure, and one is mysteriously undetected even though its optical properties suggest that it should produce a detectable lensing signal. Taken together, these results underscore the need for more extensive comparisons among different methods of massive cluster identification., Comment: 34 pages, 16 figures, ApJ accepted

The Smithsonian Hectospec Lensing Survey (SHELS) is a window on the star formation history over the last 4 Gyr. SHELS is a spectroscopically complete survey for Rtot < 20.3 over 4 square degrees. We use the 10k spectra to select a sample of pure star forming galaxies based on their Halpha emission line. We use the spectroscopy to determine extinction corrections for individual galaxies and to remove active galaxies in order to reduce systematic uncertainties. We use the large volume of SHELS with the depth of a narrowband survey for Halpha galaxies at z ~ 0.24 to make a combined determination of the Halpha luminosity function at z ~ 0.24. The large area covered by SHELS yields a survey volume big enough to determine the bright end of the Halpha luminosity function from redshift 0.100 to 0.377 for an assumed fixed faint-end slope alpha = -1.20. The bright end evolves: the characteristic luminosity L* increases by 0.84 dex over this redshift range. Similarly, the star formation density increases by 0.11 dex. The fraction of galaxies with a close neighbor increases by a factor of 2-5 for L(Halpha) >~ L* in each of the redshift bins. We conclude that triggered star formation is an important influence for star forming galaxies with Halpha emission., Comment: 26 pages, 23 figures, submitted to ApJ; version with high resolution figures available at http://www.cfa.harvard.edu/~ewestra/publications/

We describe techniques for photometric calibration of optical spectra obtained with the MMT's fiber-fed spectrograph, Hectospec. The atmospheric dispersion compensation prisms built into the MMT's f/5 wide field corrector effectively eliminate errors due to differential refraction, and simplify the calibration procedure. The procedures that we describe here are applicable to all 220,000+ spectra obtained to date with Hectospec because the instrument response is stable. We estimate the internal error in the Hectospec measurements by comparing duplicate measurements of $\sim$1500 galaxies. For a sample of 400 galaxies in the Smithsonian Hectospec Lensing Survey (SHELS) with a median z=0.10, we compare line and continuum fluxes measured by Hectospec through a 1.5 arcsec diameter optical fiber with those measured by the Sloan Digital Sky Survey (SDSS) through a 3 arcsec diameter optical fiber. Agreement of the [OII] and H alpha SHELS and SDSS line fluxes, after scaling by the R band flux in the different apertures, suggests that the spatial variation in star formation rates over a 1.5 to 3 kpc radial scale is small. The median ratio of the Hectospec and SDSS spectra, smoothed over 100 Angstrom scales, is remarkably constant to ~5% over the range of 3850 to 8000 Angstroms. Offsets in the ratio of the median [OII] and H alpha fluxes, the equivalent width of H delta and the continuum index d4000 are a few percent, small compared with other sources of scatter.

We present results from 1078 high resolution spectra of 990 stars in the young open cluster NGC 2264, obtained with the Hectochelle multiobject echelle spectrograph on the 6.5m MMT. We confirm 471 stars as members, based on their radial velocity and/or H-alpha emission. The radial velocity distribution of cluster members is non-Gaussian with a dispersion of approx 3.5 km/s. We find a substantial north-south velocity gradient and spatially coherent structure inthe radial velocity distribution, similar to that seen in the molecular gas in the region. Our results suggest that there are at least three distinguishable subclusters in NGC 2264, correlated with similar structure seen in 13CO emission, which is likely to be a remnant of initial structure in this very young cluster. We propose that this substructure is the result of gravitational amplification of initial inhomogeneities during overall collapse to a filamentary distribution of gas and stars, as found in simulations by Burkert & Hartman (2004)., Comment: 15 pages, 7 figures, 4 tables

Surface brightness is a fundamental observational parameter of galaxies. We show, for the first time in detail, how it can be used to obtain photometric redshifts for galaxies, the $\mu$-PhotoZ method. We demonstrate that the Tolman surface brightness relation, $\mu \propto (1+z)^{-4}$, is a powerful tool for determining galaxy redshifts from photometric data. We develop a model using $\mu$ and a color percentile (ranking) measure to demonstrate the $\mu$-PhotoZ method. We apply our method to a set of galaxies from the SHELS survey, and demonstrate that the photometric redshift accuracy achieved using the surface brightness method alone is comparable with the best color-based methods. We show that the $\mu$-PhotoZ method is very effective in determining the redshift for red galaxies using only two photometric bands. We discuss the properties of the small, skewed, non-gaussian component of the error distribution. We calibrate $\mu_r, (r-i)$ from the SDSS to redshift, and tabulate the result, providing a simple, but accurate look up table to estimate the redshift of distant red galaxies., Comment: Accepted for publication in the Astronomical Journal

The XBootes Survey is a 5-ks Chandra survey of the Bootes Field of the NOAO Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest (9.3 deg^2), contiguous region imaged in X-ray with complementary deep optical and near-IR observations. We present a catalog of the optical counterparts to the 3,213 X-ray point sources detected in the XBootes survey. Using a Bayesian identification scheme, we successfully identified optical counterparts for 98% of the X-ray point sources. The optical colors suggest that the optically detected galaxies are a combination of z<1 massive early-type galaxies and bluer star-forming galaxies whose optical AGN emission is faint or obscured, whereas the majority of the optically detected point sources are likely quasars over a large redshift range. Our large area, X-ray bright, optically deep survey enables us to select a large sub-sample of sources (773) with high X-ray to optical flux ratios (f_x/f_o>10). These objects are likely high redshift and/or dust obscured AGN. These sources have generally harder X-ray spectra than sources with 0.1

The Smithsonian Hectospec Lensing Survey (SHELS) combines a large deep complete redshift survey with a weak lensing map from the Deep Lens Survey (Wittman et al. 2002; 2005). We use maps of the velocity dispersion based on systems identified in the redshift survey to compare the three-dimensional matter distribution with the two-dimensional projection mapped by weak lensing. We demonstrate directly that the lensing map images the three-dimensional matter distribution obtained from the kinematic data., Comment: Astrophysical Journal Letters 9pages, 3 figures, accepted, corrected typos

The Hectospec is a 300 optical fiber fed spectrograph commissioned at the MMT in the spring of 2004. A pair of high-speed six-axis robots move the 300 fiber buttons between observing configurations within ~300 s and to an accuracy ~25 microns. The optical fibers run for 26 m between the MMT's focal surface and the bench spectrograph operating at R~1000-2000. Another high dispersion bench spectrograph offering R~5,000, Hectochelle, is also available. The system throughput, including all losses in the telescope optics, fibers, and spectrograph peaks at ~10% at the grating blaze in 1" FWHM seeing. Correcting for aperture losses at the 1.5" diameter fiber entrance aperture, the system throughput peaks at $\sim$17%. Hectospec has proven to be a workhorse instrument at the MMT. Hectospec and Hectochelle together were scheduled for 1/3 of the available nights since its commissioning. Hectospec has returned \~60,000 reduced spectra for 16 scientific programs during its first year of operation., Comment: 68 pages, 28 figures, to appear in December 2005 PASP

We present results from a Chandra survey of the nine square degree Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists of 126 separate contiguous ACIS-I observations each of approximately 5000 seconds in duration. These unique Chandra observations allow us to search for large scale structure and to calculate X-ray source statistics o ver a wide, contiguous field of view with arcsecond angular resolution and uniform coverage. Optical spectroscopic follow-up observations and the rich NDWFS data set will allow us to identify and classify these X-ray selected sources. Using wavelet decomposition, we detect 4642 point sources with n $\ge$ 2 counts. In order to keep our detections ~99% reliable, we limit our list to sources with n $\ge$ 4 counts. The full 0.5--7 keV band n $\ge$ 4 count list has 3293 point sources. In addition to the point sources, 43 extended sources have been detected consistent, with the depth of these observations and the number counts of clusters. We present here the X-ray catalog for the XBootes survey, including source positions, X-ray fluxes, hardness ratios and their uncertainties. We calculate and present the differential number of sources per flux densit y interval, $N(S)$, for the point sources., Comment: 1 Long table, 12 figures,28 pages

We obtained a 5 ksec deep Chandra X-ray Observatory ACIS-I map of the 9.3 square degree Bootes field of the NOAO Deep Wide-Field Survey. Here we describe the data acquisition and analysis strategies leading to a catalog of 4642 (3293) point sources with 2 or more (4 or more) counts, corresponding to a limiting flux of roughly 4(8)x10^{-15} erg cm^{-2}s^{-1} in the 0.5-7 keV band. These Chandra XBootes data are unique in that they consitute the widest contiguous X-ray field yet observed to such a faint flux limit. Because of the extraordinarily low background of the ACIS, we expect only 14% (0.7%) of the sources to be spurious. We also detected 43 extended sources in this survey. The distribution of the point sources among the 126 pointings (ACIS-I has a 16 x 16 arcminute field of view) is consistent with Poisson fluctuations about the mean of 36.8 sources per pointing. While a smoothed image of the point source distribution is clumpy, there is no statistically significant evidence of large scale filamentary structure. We do find however, that for theta>1 arcminute, the angular correlation function of these sources is consistent with previous measurements, following a power law in angle with slope -0.7. In a 1.4 deg^{2} sample of the survey, approximately 87% of the sources with 4 or more counts have an optical counterpart to R ~26 mag. As part of a larger program of optical spectroscopy of the NDWFS Bootes area, spectra have been obtained for \~900 of the X-ray sources, most of which are QSOs or AGN., Comment: 18 Pages, 10 figures (AASTex Preprint format)

The Ohara glass S-FTM16 is of considerable interest for near-infrared optical designs because it transmits well through the K band and because negative S-FTM16 elements can be used to accurately achromatize positive calcium fluoride elements in refractive collimators and cameras. Glass manufacturers have sophisticated equipment to measure the refractive index at room temperature, but cannot typically measure the refractive index at cryogenic temperatures. Near-infrared optics, however, are operated at cryogenic temperatures to reduce thermal background. Thus we need to know the temperature dependence of S-FTM16's refractive index. We report here our measurements of the thermal dependence of S-FTM16's refractive index between room temperature and ~77 K. Within our measurement errors we find no evidence for a wavelength dependence or a nonlinear temperature term so our series of measurements can be reduced to a single number. We find that Delta n_{abs} / Delta T = -2.4x10^{-6} K^{-1} between 298 K and ~77 K and in the wavelength range 0.6 micron to 2.6 micron. We estimate that the systematic error (which dominates the measurement error) in our measurement is 10%, sufficiently low for most purposes. We also find the integrated linear thermal expansion of S-FTM16 between 298 K and 77 K is -0.00167 m m^{-1}., Comment: 8 pages, including 9 figures. Uses emulateapj.cls. Accepted for publication in PASP

Refractive optics in astronomical instruments are potentially sensitive to temperature gradients and temperature transients. This sensitivity arises from thermally dependent refractive indices, lens spacings, and lens dimensions. We have therefore undertaken a detailed thermal analysis of Binospec, a wide-field optical spectrograph under development for the converted MMT. Our goals are to predict the temperature gradients that will be present in the Binospec optics and structure under realistic operating conditions and to determine how design choices affect these gradients. We begin our analysis by deriving thermal time constants for instrument subassemblies. We then generate a low-resolution finite difference model of the entire instrument and high-resolution models of sensitive subassemblies. This approach to thermal analysis is applicable to a variety of other instruments. We use measurements of the ambient temperature in the converted MMT's dome to model Binospec's thermal environment. During moderate conditions we find that the Binospec lens groups develop 0.14 C axial and radial temperature gradients and that lens groups of different mass develop 0.5 C temperature differences; these numbers are doubled for the extreme conditions. Internal heat sources do not significantly affect these results; heat flow from the environment dominates. The instrument must be periodically opened to insert new aperture masks, but we find that the resulting temperature gradients and thermal stresses in the optics are small. Image shifts at the detector caused by thermal deflections of the Binospec optical bench structure are approx 0.1 pixel/hr. We conclude that the proposed Binospec design has acceptable thermal properties, and briefly discuss design changes to further reduce temperature gradients., Comment: 11 pages, to appear in PASP v114 Dec 2002

We discuss the design of an inexpensive, high-throughput CCD spectrograph for a small telescope. By using optical fibers to carry the light from the telescope focus to a table-top spectrograph, one can minimize the weight carried by the telescope and simplify the spectrograph design. We recently employed this approach in the construction of IntroSpec, an instrument built for the 16-inch Knowles Telescope on the Harvard College campus., Comment: 17 pages including 7 figures, PASP, accepted (higher resolution figures at http://cfa-www.harvard.edu/~sheila/introspec.ps.gz)